Conventionally, to extracorporeally circulate blood during hemodialysis, a method, with which two medical puncture needles of 14 to 19 gauge having a sharp tip are inserted into so-called blood accesses provided in a patient's arm for securing routes for the arterial side and for the venous side, for drawing blood out of the body through a blood circuit including these routes has been widely used.
As a medical puncture needle, that of indwelling type 1, as shown in FIG. 9, with which a tubularly formed hollow metal needle is used, being kept inserted into the human body, has long been known, however, that of outer tube-indwelling type 2 that is formed to have a dual-tube structure consisting of an outer tube needle 3 and an inner needle 4, as shown in FIG. 10, which are inserted into a blood vessel together before the inner needle 4 is removed, and then the outer tube needle 3 alone is kept inserted and retained in the blood vessel, has been in wide spread use. More recently, the medical needle of outer tube-indwelling type 5, with which an inner needle 6 is formed to be solid rather than tubular, being made of metal, as shown in FIG. 11, has also been known.
With any of said medical puncture needles of type 1, 2, 5, the tip portion of the needle (inner needle) 1, 4, 6 has been formed to be sharp so as to pierce the skin or a blood vessel of a patient, and typically the tip portion of the needle (inner needle) 1, 4, 6 has been cut off at an oblique angle with respect to the direction of the axis, as shown in FIG. 9 to FIG. 11, and provided with an edge 7 steeply sloping down toward the needlepoint thereof.
However, with conventional medical puncture needles 1, 2, 5, as described above, a thick needle of 14 to 19 gauge in diameter size is used in order to secure the blood flow rate required for hemodialysis (200 to 300 mi/mm), and thus there is a problem that the patient is forced to endure the pains involved in creating a puncture (boring pains) at every dialysis session carried out two or three times a week, for example.
Further, the tip portion of the needle (inner needle) 1, 4, 6 has a sharp edge 7 sloping down toward the needlepoint in order to facilitate the insertion into the skin and a blood vessel wall, as described above, thus there has been a possibility that, if the thick hollow needle 1, 4 is used, so-called coring may occur at the time of puncture, causing a part of the living tissue in the skin or a blood vessel to be scraped off into the hollow needle 1, 4 and flow into the blood vessel. Further, because the tip is sharp, a mere touch with the needle has tended to cause wrong puncture, and thus puncture troubles due to such wrong puncture, such as subcutaneous bleeding, could not have been effectively avoided, giving patients pain.
Further, the repetition of puncturing scrapes off and thus damages the tissue at the puncture site in the so-called blood accesses, hardens the living tissue, and forms swelling, leading to reduction in the service life of the blood accesses. Still further, there has been a problem that, when a blood access formed with an artificial blood vessel is punctured, puncturing in the same part must be avoided because an artificial blood vessel is slow to recover from the damage given to it at a puncture site, and thus many holes have been made in the patient's blood vessel every time dialysis is carried out, forcing the patient to endure further pains.
Further, although a needle which has been removed from a patient is subjected to disposal, a health-care worker might accidentally touch the sharp needlepoint thereof, getting injured, resulting in an infection accident, thus the necessity of eliminating such problem has been presented.
Being developed in consideration of the problems of the prior arts as described above, the purpose of the present invention is to provide a medical needle which can greatly reduce the pains involved in creating a puncture, avoid subcutaneous bleeding and damage to blood vessel walls by preventing wrong puncture, eliminate the possibility that coring may occur, causing further damage to the living tissue and a part of the living tissue to flow into a blood vessel, and prevent infection accidents due to wrong puncture, thus assuring a high level of safety of health-care workers.